{

    // 给类型string取名字叫s
    // 1. 别名
    // 2. 建立了新的类型
    type s = string
    
    let a: string = '123'

    let b: s = '123'



    // let arr1: (number|string)[] = [1,'a']

    // let arr2: (number|string)[] = [1,'a']

    type Ns = (number | string) []


    let arr1: Ns = [1,'a',false]

    let arr2: Ns = [1,'a']



}
